The SWEET proteins are a group of sugar transporters that play a role in sugar efflux during a range of biological processes, including stress responses. However, there has been no comprehensive analysis of the SWEET family genes in Brassica oleracea (BoSWEET), and the evolutionary pattern, phylogenetic relationship, gene characteristics of BoSWEET genes and their expression patterns under biotic and abiotic stresses remain largely unexplored. A total of 30 BoSWEET genes were identified and divided into four clades in B. oleracea. Phylogenetic analysis of the BoSWEET proteins indicated that clade II formed first, followed by clade I, clade IV and clade III, successively. Clade III, the newest clade, shows signs of rapid expansion. The Ks values of the orthologous SWEET gene pairs between B. oleracea and Arabidopsis thaliana ranged from 0.30 to 0.45, which estimated that B. oleracea diverged from A. thaliana approximately 10 to 15 million years ago. Prediction of transmembrane regions showed that eight BoSWEET proteins contain one characteristic MtN3_slv domain, twenty-one contain two, and one has four. Quantitative reverse transcription-PCR (qRT-PCR) analysis revealed that five BoSWEET genes from clades III and IV exhibited reduced expression levels under chilling stress. Additionally, the expression levels of six BoSWEET genes were up-regulated in roots of a clubroot-susceptible cabbage cultivar (CS-JF1) at 7 days after inoculation with Plasmodiophora brassicae compared with uninoculated plants, indicating that these genes may play important roles in transporting sugars into sink roots associated with P. brassicae colonization in CS-JF1. Subcellular localization analysis of a subset of BoSWEET proteins indicated that they are localized in the plasma membrane. This study provides important insights into the evolution of the SWEET gene family in B. oleracea and other species, and represents the first study to characterize phylogenetic relationship, gene structures and expression patterns of the BoSWEET genes. These findings provide new insights into the complex transcriptional regulation of BoSWEET genes, as well as potential candidate BoSWEET genes that promote sugar transport to enhance chilling tolerance and clubroot disease resistance in cabbage.

Sugar transporter protein (STP) genes are involved in multiple biological processes, such as plant responses to various stresses. However, systematic analysis and functional information of STP family genes in Brassica oleracea are very limited. A comprehensive analysis was carried out to identify BoSTP genes and dissect their phylogenetic relationships and to investigate the expression profiles in different organs and in response to the clubroot disease. A total of 22 BoSTP genes were identified in the B. oleracea genome and they were further classified into four clades based on the phylogenetic analysis. All the BoSTP proteins harbored the conserved sugar transporter (Sugar_tr, PF00083) domain, and the majority of them contained 12 transmembrane helices (TMHs). Rates of synonymous substitution in B. oleracea relative to Arabidopsis thaliana indicated that STP genes of B. oleracea diverged from those of A. thaliana approximately 16.3 million years ago. Expression profiles of the BoSTP genes in different organs derived from RNA-Seq data indicated that a large number of the BoSTP genes were expressed in specific organs. Additionally, the expression of BoSTP4b and BoSTP12 genes were induced in roots of the clubroot-susceptible cabbage (CS-JF1) at 28 days after inoculation with Plasmodiophora brassicae, compared with mock-inoculated plants. We speculated that the two BoSTPs might be involved in monosaccharide unloading and carbon partitioning associated with P. brassicae colonization in CS-JF1. Subcellular localization analysis indicated that the two BoSTP proteins were localized in the cell membrane. This study provides insights into the evolution and potential functions of BoSTPs.

Plastic film mulching is a common practice to increase vegetable yields. However, the effects of plastic mulch films on different vegetable fields remain largely unknown. In the current study, biodegradable mulch films (BDMs) and polyethylene mulch films (PEMs) were used to explore their effects on three vegetable fields (broccoli, chili pepper and garlic). Compared with bare soil, both BDMs and PEMs could effectively maintain higher exchangeable potassium contents in rhizosphere soil, and significantly increase various soil properties and microbial abundance both in rhizosphere and non-rhizosphere soils. In terms of yields, the treatments of BDMs and PEMs effectively increased broccoli, chili pepper and garlic yields by 17.6–19.0%, 21.3–23.3% and 26.0–29.5%, respectively, when compared with the bare soil. Our initial characterization provided insights into the effects of BMDs and PEMs on soil properties, yields and diversity of rhizosphere and non-rhizosphere microbial communities in three vegetable fields.

Basic helix–loop–helix (bHLH) transcription factor (TF) family is commonly found in eukaryotes, which is one of the largest families of regulator proteins. It plays an important role in plant growth and development, as well as various biotic and abiotic stresses. However, a comprehensive analysis of the bHLH family has not been reported in Brassica oleracea. In this study, we systematically describe the BobHLHs in the phylogenetic relationships, expression patterns in different organs/tissues, and in response to chilling stress, and gene and protein characteristics. A total of 234 BobHLH genes were identified in the B. oleracea genome and were further clustered into twenty-three subfamilies based on the phylogenetic analyses. A large number of BobHLH genes were unevenly located on nine chromosomes of B. oleracea. Analysis of RNA-Seq expression profiles revealed that 21 BobHLH genes exhibited organ/tissue-specific expression. Additionally, the expression of six BobHLHs (BobHLH003, -048, -059, -093, -109, and -148) were significantly down-regulated in chilling-sensitive cabbage (CS-D9) and chilling-tolerant cabbage (CT-923). At 24h chilling stress, BobHLH054 was significantly down-regulated and up-regulated in chilling-treated CS-D9 and CT-923. Conserved motif characterization and exon/intron structural patterns showed that BobHLH genes had similar structures in the same subfamily. This study provides a comprehensive analysis of BobHLH genes and reveals several candidate genes involved in chilling tolerance of B. oleracea, which may be helpful to clarify the roles of bHLH family members and understand the regulatory mechanisms of BobHLH genes in response to the chilling stress of cabbage.

Squamosa promoter-binding protein-like (SPL) is a major family of plant-specific transcription factor, which is involved in multiple biological processes, such as plant growth and development, hormone response, light response and stress response. Therefore, it has been profoundly significant to systematically analyze the SPL Transcription Factors family in Brassica oleracea. In this study, a total of 33 BoSPLs were identified in the B. oleracea genome, and they were further divided into six subgroups based on the phylogenetic tree constructed from the SPL proteins of B. oleracea, B. rapa and Arabidopsis thaliana. The expression profile of BoSPLs in different organs/tissues showed that a large number of BoSPLs were expressed in the callus, root, stem, leaf, bud, flower and silique. In addition, the expression levels of two BoSPLs (BoSPL9b and BoSPL10b) were up-regulated in chilling tolerance cabbage ‘CT-923’ at 6 h after chilling stress when compared with normal treatment (mock), while two BoSPLs (BoSPL9b and BoSPL15a) in chilling sensitive cabbage ‘CS-D9’, five BoSPLs (BoSPL1, -9a, -9b, -10b, -11b) in ‘CT-923’ and two BoSPLs (BoSPL9b and BoSPL16a) in ‘CS-D9’ were up-regulated after 24 h chilling stress, indicated that these genes may play an important role in the chilling-tolerance of cabbage. We analyzed the characteristics of BoSPLs and provided the basis for further functional research.

Plasmodiophora brassicae Woronin, the pathogen responsible for clubroot, poses a major threat to the production of cruciferous crops worldwide. The clubroot disease creates swollen, club-shaped galls on roots, which disrupt water and nutrient transport, leading to stunted plant growth or, in severe cases, plant death. Its widespread distribution and severe economic consequences underscore the urgent need for a deeper understanding of this notorious plant disease. In this review, we synthesize recent advances in understanding the life cycle, genome, and effector biology of the clubroot pathogen, as well as progress in elucidating the clubroot resistance of cruciferous plants. We also discuss persistent challenges and outline future research priorities aimed at unraveling the molecular basis of interactions between P. brassicae and its cruciferous hosts. Such insights may facilitate the development of more effective and sustainable strategies for controlling clubroot.